Apparatus for training aircraft personnel in radio navigation



Oct. 18, 1949. A. P. STUHRMAN EI'AL 2,485,331

APPARATUS FOR TRAINING AIRCRAFT PERSONNEL IN RADIO NAVIGATION Fil'edNov. 25, 1939 9 Sheets-Sheet 1 FIG. 1.

INVENTORS.

Ahler'I" P. EL'uhrm-an Charles W. MC'KEE ATTORN EYS.

Oct. 18, 1949. A. P. STUHRMAN EI'AL 2,485,331

APPARATUS FOR TRAINING AIRCRAFT PERSONNEL 1N RADIO NAVIGATION Filed Nov.25, 1939 9 SheetsSheet 2 Ahlerf' P. Eflfuhr'man Charles W. M KeeATTORNEYS.

Z5 INVENTORS A. P. STUHRMAN ET AL APPARATUS FOR TRAINING AIRCRAFTPERSONNEL IN RADIO NAVIGATION Oct. 18,1949;

9 Sheets-Sheet 3 Filed Nov. 25, 1939 INVENTOR5. STu'hr m an MF' K2 EARIEL-'1'. P. Eh ar'l a 5 W 24* &; ATTORNEYS.

Oct. 18, 1949'. A. P. STUHRMA-N r:rA| 2,435,331

APPARATUS FOR TRAINING AIRCRAFT PERSONNEL IN RADIO NAVIGATION Filed NOV.25, 1939 9 Sheets-Sheet 4 INVENTORS. A111 2 F1 1 Eltuhrm an Charles W.ME'KEE.

BY f? Oct. 1 8, 1949. A. P. .s'ru-HRM-AN "ETM: 2,485,331

APPARATUS .FQR TRAINING AIRCRAFT PERSONNEL IN RADIO NAVIGATION FiledNov. 25, 1939 9 Sheets-Sheet 5 FIG. 9.

m mmlluummu 40 /30 \flf FIG. 10.

INVENTORS.

Ah'ler'i' .P. Ell'uhrman Char-la a W. M Kee ATTORNEYS.

Oct. 18, 1949. A. P. STUHR'MANA ETAL 2,485,331

APPARATUS FOR TBAININQAIRCRAFT PERSONNEL IN RADIO NAVIGATION Filed Nov.25, 1939 9 Sheets-Sheet 6 FIG. 11.

4/ M I! Q I l 7d] H g INVENTORS Ahler'i' P. Eflfuhrman Charles. WM K22BY 2 Q/ Z OM ATTORNEYS.

00L 1949. A. P. STUHRMAN- ETAL APPARATUS EGR .TRKINING AIRCRAFTPERSONNEL IN RADIO NAVIGATION 9 Sheets-Sheet 7 Filed Nov. 25, 1939 FIG.1 3.

INVENTORS. Ahlevi? P. EIfuhrman Charles W. M Ke E Oct. 18, 1949. r A.as'ruHaMAN ETAL 2,485,331

AYYNRATUS FOR TRAINING AIRCRAFT PERSONNEL IN RADIO NAVIGATION 9Sheets-Sheet 8 Filed Nov. 25:, 1959 TRAINER Humans 350 Ann Bumme IIITRAINER HEADING INVENTORS A111 E :3: F. 'Ext'uhrman Charles W M 'KE Eam, ATTORNEYS.

Oct. 18, 1949.

A. P.-STUHFMAN ET AL 2,485,331 APPARATUSIFOR TRAINING AIRCRAFT PERSONNELIN RADIO NAVIGATION 9 Sheets-Sheet 9 Filed Nov 25,, 1939 Fusr-rr EnuRsEEmu: 5:111:45

Ann Azmu'rH Rename Fun humus 520 Bsnmus ||e CnuRSE 75 FLIGHT EDuRSE Emu:SETTING Ann AZIMUTH READING FDR fiEARma nu KW BEARINB 12 5 DIFFERENIIE135 EounsE HEADING sad INVENTORS ATILEPT F. SCuhrman Charles W. MGK'EEATTORNEYS.

.sion of an improved Patented Oct. 18, 1949 APPARATUS FOR TRAININGAIRCRAFT PER- SONNEL IN RADIO NAVIGATION Ahlert P. Stuhrman, Kee,Hialeah, Fla.,

New York Miami, and Charles w. Mcassignorsyby mesne assignments, to LinkAviation,

Inc., a corporation of Application November 25, 1939, Serial No. 306,188

11 Claims.

This invention relates to improvements in methods and apparatus forteaching the art of radio and instrument flying while on the ground.

The primary object of the invention is the provision of improvedelectrical means associated with an aircraft training device forinstructing pilots and student aviators the art of blind flight.

A further object of this invention is the provision of improved meansassociated with an aviation trainer, commonly known as the Linkinstrument and radio pilot trainer, such as is detailed, as tostructural features, in U. S. Patents #'1,825,462; 2,099,857, and2,119,083, but embodying improved means thereover for training studentsand other pilots the art of radio navigation.

A further object of the invention relates to improved electricalsignalling apparatus associated with ground aircraft training apparatus,for determining bearings from an unknown position to agiven transmittingstation or to more than one transmitting station; the resultingknowledge enabling the aerial navigator to determine his exact locationand proceed to a given point for landing.

A further object of the invention is the provision of improved apparatusassociated with a ground trainer, such as is set forth in U. 8. Patents1,825,462 and 2,099,857 for instructing ground personnel in the art ofradio navigation and radio direction finding.

- A further object of this invention is the provision of improvedelectrical signalling apparatus adapted for. installation upon aircraftground trainers, such as the Link" trainer, wherein the instrumentsemployed simulate those of an actual radio direction finder, thusenabling the student to become skilled in radiodirection finding.

A further object of this invention is the provision of improvedapparatus adapted for association with ground training apparatus whichoperates, so far as the student or pilot is concerned, identically thesame as a looped direction finder on aircraft in flight; the apparatusincluding an instructor's unit which will enable the instructor topresent various problems to the pilot for solution, and visuallyunderstand the pilot's response thereto.

A further object of this invention is the proviartiflcial radiodirection finder adapted for association with ground training apparatus,such as that known as the Link" trainer; the same including an azimuthindicator for the pilot and a complementary unit for the instructoroutside of the trainer; the azimuth indicator and instructors unithaving associated therewith electrical signalling apparatus which willenable the instructor to present to the pilot various problems forsolution, such as station finding, positioning location, and other radionavigation problems; the instructor's unit having means for automaticoperation so that the course theoretically pursued by the pilot may berecorded on a chart or range finding map.

A further object of this invention is the provision of an improvedattachment adapted to be associated with a flight log or automaticrecorder of the Link trainer type, which renders the flight course scaleof the automatic recorder automatic in operation.

Other objects and advantages of this invention will be apparent duringthe course of the following detailed description.

In the accompanying drawings, forming a part of this specification, andwherein similar reference characters designate corresponding partsthroughout the several views,

Figure 1 shows student and pilot ground aircraft training apparatusincluding a pilot trainer and automatic recorder in which our improvedinvention is installed. I

Figure 2 is a diagrammatic representation of the basic circuit andelectrical apparatus associated with our invention and with the Link"adaptation circuit diagram.

Figures 3, 4, and 5 are fragmentary views of improved means forrendering the flight course scale of the automatic recorder fullyautomatic in operation; that is, the instructor does not have to resetthe flight course scale in response to changes in position by the pilot.

Figure 6 is a perspective view, partly diagrammatic, showing thecooperative pilot controlled azimuth indicator and the instructorsautomatic recorder, with the improved electrical signalling apparatus ofour invention associated with these two units.

Figure '7 is a front elevation of the azimuth indicator.

Figure 8 is a side view of the azimuth indicator with the improvedfeatures of our invention associated therewith.

Figure 9 is a side azimuth indicator.

Figure 10 is a bottom plan view of the improved azimuth indicator.

Figure 11 is a cross sectional view taken through the automaticrecording device showing more particularly the coil arrangement of avariable coupling transformer which is used in connection elevation ofthe improved 3 with the improved electrical signalling apparatus of thisinvention.

Figure 12 is a vertical sectional view taken through the flight coursescale of the automatic recorder, and showing improved features of thisinvention associated therewith, particularly the transformer coils' andassociated contacts.

Figure 13 is a vertical sectional view taken thru the transformer coilarrangement of the automatic recorder along the axis of the tracer wheelshaft.

Figure 14 is a diagrammatic representation of a problem set-up, showingthe complementary azimuth scale and flight course scale readings inassociation with the plotted theoretical course of the pilot on a radiorange chart or map.

Figure 15 shows a second problem set-up with the complementary readingsof the azimuth scale and flight course scale in relation to radio rangecharts designating two radio range stations.

In the drawings, wherein for the purpose of illustration is shown only apreferred embodiment of the invention, the letter A may generallydesignate a ground trainer, such as the Link type. with which isassociated an automatic recorder or flight log device; the same beingwell known in construction, except for improved features to behereinafter described, and operating to trace the theoretical flightcourse of the pilot within the trainer.

The trainer A, as above mentioned, is described in detail in such U. S.patents as 1,825,462 and 2,099,857, although it is to be understood thatthe loop direction finding characteristics of this invention areapplicable to other training devices.

The trainer A, as is well known, includes a stationary base on which thefuselage 2| is mounted. The latter has a universal Joint mounting ormechanism in the base so that it can rotate through 360, comparable tothe yawning motion of an airplane. The motions of the trainer, as iswell known, are obtained by use of reduced air pressure or partialvacuum and operate various bellows for the trainer to simulate pitch,climb. bank or roll, and turning or ya Air control of the operatingmechanism provides a variable power source which is controlled entirelyby the stick and rudder within the fuselage through valve mechanismswhich create motion of the fuselage about the three axes of the trainer,in exact simulation of aircraft flight movement.

The flight log or automatic recorder B, so far as conventional featuresare concerned is generally of the nature set forth in U. S. Patent#2,l79,663, and includes upper and lower triangular platform plates and28 suitably connected together in spaced relation. They are mounted upona pair of driving wheels 21, and a third wheel 28 known as the tracerwheel, which is mounted on the lower end of a rotatable shaft 29. Theinstrument travels on these three wheels, which are all connectedtogether by gearing 80 between the plates .25 and 28, so thatdirectional control is effective with all three wheels at the same timefrom one master synchronous reversible motor. Power is supplied fordriving forward by two constant speed synchronous motors connected tothe two driving wheels 21. The third wheel 28 is of course an idlerwheel and supplied with an ink roller II for marking on the chart thetheoretical course of the trainer.

The automatic recorder synchronous motor is an "autosyn motor. The other"autosyn" motor the purpose of moving I ferred that the spacing andwhich directs the motion or rotation of the automatic recorder motor islocated in the base of the trainer A. Rotation of the fuselage 2|rotates the column which in turn rotates the "autosyn motor of thetrainer through a gear train. The "autosyn" motor of the recorder isconnected electrically to the "autosyn" motor of the trainer so that anyrotation of the "autosyn motor of the trainer will cause a correspondingrotation of the "autosyn motor on the recorder. The gear mechanism ofthe recorder is such that any movement of the wheel .controlled by therecorder motor causes a corresponding move- .ment of the other twowheels by means of three gears of equal diameter meshed with a commongear to which the "autosyn motor of the recorder is attached. Gearreduction makes possible several settings, of the automatic recorder,but relative movement is always constant. The automatic recorder doesnot turn. The driving wheels 21 and also the tracer wheel 28 turn togive directive travel to the recorder across a map. These are of courseall conventional features and will be understood by those skilled in theart to which this invention relates.

Referring to the basic circuit diagram of our invention, as shown inFigure 2 of the drawings, two variable coupling transformers areprovided, one on the automatic recorder of the instructor's unit, andthe other in association with the azimuth indicator C under control ofthe pilot in the fuselage of the trainer. These transformers areconnected to each other by wiring; the idea being that of conveyingsignal voltage from one transformer to the other.

The automatic recorder transformer 48, designated in Figure 2, is madeup of three coils 4|, 42, and 43; the coils 42 and 43 being mounted inan angular relation of with respect to the fixed point at a given radiuswhereat the coil 4| is mounted. This coil 4|, as will hereinafter bedetailed, is mounted to rotate on its own axis, which is the commonpoint of intersection of the axes of the other coils 42 and 43. Thecoils 42 and 48 are mounted on a rotatable base 44 as will behereinafter described.

The transformer 41 forming part of the azimuth indicator C consists ofcoils 48, 48 and 58. Coils 48 and 50 are rigidly mounted to a panel ofthe azimuth indicator C, but the coil 48 is attached to the main shaftof the azimuth indicator and turns therewith as will be subsequent- 1ydescribed. Coils 49 and 58 are disposed with their axes at an angleof-90 with respect to each other, and the intersectin point of theseaxes is the point of rotation of 'the coil 48. It is presize of thecoils of the two transformers be identical.

In the wiring diagram shown in Figure 2,- 5| designates the variousterminal blocks, contacts, cables, etc. to be subsequently described indetailing the construction and installation of the unit in the azimuthindicator and automatic recorder. As shown in Figure 2 the coils 42 and43 of the are connected to the coils 48 and 50 bymeans of three wires52, 53, and 54; the common lead wire 53 making only three wiresnecessary to connect the two sets of coils. The coil 4| of the automaticrecorder transformer is connected by wiring to the standard radio rangesignalling device designated at 55 in the drawings, which may be anytype of oscillator, or any other approved signal source. This signallingsource 55 is known in the Link trainer as the Link radio range controlunit and amplifier."

The wiring may have a D. F. amplifier 89 therein.

The coil 48 of the transformer unit 41 associated with the azimuthindicator is connected by wiring 59 with the headset 89 of the pilot,and the wiring may have a trainer D. F. amplifier 9| located therein,with suitable volume control 92. The dotted lines 92' shown in Figure 2of the drawings designate wiring which may be connected between theinstructor's monitoring headset 83 and the student headset 89.

In operation, the coil 48 picks up signal voltage through thetransformer 41 when the coil 4| of the transformer 49 is excited. Thesame signal level is obtained by the coil 48 as transmitted by the coil4I because the coils are in the same relative position in bothtransformer units. The magnitude of induced voltage is measured by theangle of the axis of the coil 4| with respect to the coils 42 and 48.Voltages in coils 42 and 49 have a definite phase relation with respectto each other and with respect to the voltage in the coil 4|; thevoltages in these coils 42 and 43 being reproduced across the coils 49and 59. Of course any change in the voltage relation of coils 42 and 43will likewise produce a corresponding change in coils 4.9 and 59. Thus,any change in the relative position of coil 4| with respect to the coils42 and 43 will result in a corresponding change in voltage in the coil48.

In direction finding work it is desirable, and considered more accurate,particularly for aural detection, to observe the null or zero signalpoint. This condition is obtained by movement of the coil 48 through anangle of 90 from the position of maximum response. In this position thecurrents from coils 49 and 59 produce voltages in coil 48 which areopposite in phase and hence cancelled. Of course the magnitude of thisvoltage is controlled by the relative position that the coil 4I bears tothe coils 42 and 49.

Referring to the transformer mounting and operation, as applied to theautomatic recorder, the tracer wheel 28 of the automatic recorder ismounted on a shaft 29 which is rotatably mounted in the frame 25 of theautomatic recorder. The coils 42 and 43, as best illustrated in Figures12 and 13 of the drawings, are rigidly attached to a Bakelite base 44which is mounted upon and attached to a bearing sleeve or bushing 1I, sothat the said platform or base 44 may rotate about the shaft 29, as canbe understood from Figure 13 of the drawings. 6 of the drawings thecommon lead wire 53 has a contact connection 19 with the shaft 29, whichis at ground potential. The other lead wires 52 and 54 are provided withcontacts 14 and 15 respectively mounted on the automatic recorderplatform 25 and in conducting engagement with slip rings 16 and 11respectively; the latter being mounted on the bottom of a Bakelite orother insulation disc 18 which rotates with the bushing 1| to which thecoil platform 44 is attached. The slip rings 16 and 11 are respectivelywired with the coils 43 and 42, as is'shown in Figure 6 of the drawingsand the said coils have a ground connection upon the shaft 29, as hasbeen described, for the basic circuit shown in Figure 2 of the drawings.The opposite ends of the coil 4| are connected to slip rings 89 and 8|,which are on the upper and lower surfaces of an insulation base As isshown in Figure i mounting 82 for the coil 4|, as shown in Figure 13 ofthe drawings; suitable contacts 84 and 85 being provided for these sliprings 89 and 8| which are respectively wired to contact rings 81 and 88;the latter being mounted on the insulation bush- The automatic recorderincludes an inverted cap or cover 95. of any approved material which isattached to the platform 44 for rotation with the coils 42 and 48,-asshown in Figures 12 and 13 of the drawings, cover has the flight coursescale I99 indicated thereon, as shown in Figure 6, and various otherfigures of the drawings. As be fore mentioned, the coil 4|v is attachedto the tracer wheel shaft 29, and the mode of attachment is indicated inFigure 13 of the drawings at I9I; an extension of the shaft through thecoil 4| having a flight course scale pointer I95 mounted thereon andoperative over the flight course scale I99. A reference pointer I95 ismounted on the frame 25 of the automatic recorder relative to the flightcourse scale I99. as is shown in various figures of the drawings. It isof course understood that the bushing 1| rotates about the shaft 29 andthat the insulation discs and rings 44, 18 and 89 are clamped theretoand rotate with the bushing, as shown in Figure 13.

The azimuth indicator C is of unusual construction, insofar as the radioloop signal circult is concerned, since it has the coils of the pilottransformer set associated directly therewith. It includes a panel I29on which the azimuth scale |2| is delineated. The coil 48 of thetransformer unit 41 is rotatably mounted by means of a shaft I28 on theframework I24 below the panel. The shaft I29 is connected by reductiongearing I25 with a manually controllable crank I21 which is mounted onthe front of the panel I29 as is indicated in Figures 7, 8, and 9 of thedrawings. A platform I24 attached as part of the framework beneath thepanel I29, has the coils 49 and 59 fixedly attached thereto, and it isof course understood that the panel I29 is mounted on the fuselage ofthe trainer. It may be mounted vertically in front of the pilot, asindicated in Figure 1 of the drawings, although the location andposition of the azimuth indicator frame is optional. The wiring of thecoils 48, 49, and 59 is indicated in Figures 2, 6, and 10 of thedrawings, and it is indicated in the latter two figures that theopposite ends of the wiring in the coil 48 are connected by means ofterminals 539 with suitable slip rings I3I; the wires leading from theterminals I39 as'indicated at 59 in the' drawings to an amplifier andthe headset of the student.

Before detailing the method of solving range finding problems it will bewell to bear in mind that the student pilot in the trainer operates theazimuth indicator in the same manner as in actual flight. The circuitand bearings are set up by the instructor and controlled by him.Bearings may be taken through the full 360 without the use of reciprocalbearings and without having to reverse rotation of the indicator. Stopsmaybe installed to duplicate an actual installation, and the 180ambiguity exists as an all standard loop circuit.

The circuit operates on audio frequency, although radio frequencies maybe used. The signal received by the student is subject to variation inintensity'with rotation of theloop or the trainer in the same manner asthe loop circuit in actual plane installation. The signal, input isvaried through movement of the trainer because The automatic recorder isplaced on the map directly south of the radio range station. The coilsl2 and ll of the automatic recorder transformer are set to the correctposition by rotating the flight course scale casing ll so that the northis indicated by the reference pointer ill. The pilot takes a bearing onthe azimuth indicator which shows 90 to the left. Subtracted from themagnetic compass heading will give 0 north. The student then turns thetrainer 90' left from its east heading and the bearing is taken. Thereading on the azimuth-indicator Referring to the problem set up inFigure 14 the radio range map is indicated at D, and the flight coursescale and azimuth readings are indicated for the various bearingconditions by means of dot and dash lines.

The radio range map shows the courses and quadrant, and the line RSTUrepresent the path traced by the automatic recording .wheel 28.

'willbe0.

The path begins at R and ends past U. The

three points are indicated by circles in this path RSTU where bearingswere taken. and it will be noted that the dot and dash lines lead fromthese points of bearing to the various respective readings of the flightcourse and azimuth indicator scales.

In the solution of this problem the automatic recorder was placed on themap D at approximately 60. The heading of the trainer as indicated bythe arrow was 350, and of course the automatic recorder wasautomatically moved on a course of 350" at a predetermined rate. At thepoint R a bearing was of course taken. Prior to taking this bearing theinstructor set the flight course scale in the proper manner, which ofcourse consisted in moving the flight course scale with reference to thepointer I00 so as to read correctly according to the position at whichthe bearing is taken. of course the instructor must at all times movethe flight course scale casing so as to correct the reading thereon asdetermined by the extension of the radial degree lines on the radiorange map. As will be subsequently described the setting of the flightcourse scale casing I may be rendered automatic.

Continuing with a description of the problem set up in Figure 14 abearing is taken at the location 200 on the radio range map. and thetracer wheel is of course located on the extension of 52, as the mapshows. The flight course scale I00, as shown with the heading Time 1 isset by the instructor with reference to the flxed pointer It! so that itreads 52. This is of course determined by the location of the tracerwheel on the radio range map, since its positioning is automaticaccording to the position which the student pilot has moved it. Theheading of the trainer A at this instant is 350. The pilot in thetrainer takes a bearing at instant giving a resulting 118', or

62, as the azimuth indicator scale shows. The

pilot at this instant must consider the station in either direction. Thepilot may then make a left turn. which he does at the location B on thecourse shown on the radio map. of 55, and the instructor continues tocorrect the flight course scale as indicated by the position'of thetracer wheel on the radial degree lines of the range map. At thelocation 20i a second bearing is taken. The instructor has correctedtheflight course scale at this location of the tracer wheel to read 28.The heading of the trainer is 295, and the bearing observed by the piloton the azimuth scale for this "Time 2" is 92 or 88. has observed thatafter the turn at B the subtract side of the azimuth scale reading hasdecreased while the "add" side of the azimuth reading has increased,indicating to him that the station is at the left. The pilot thensubtracts 92- from the trainer heading of 295 which gives him a courseto the radio range station on the radio range map of 203. He makes thisturn as indicated at T, and after the turn has been made and the line offlight has been set a bearing is taken at the location 202 to correctfor inaccuracy in the bearing or course because of the turn. The bearingtaken at 202. after the instructor has set the flight course scalirinproper position, as indicated at Time 3 shows on the azimuth scale areading of 0. This is a homing position and of course indicates to thestudent pilot that the trainer is headed directly for the radio rangestation.

As before explained the student pilot is able to obtain a correctreading on the azimuth indicator scale by obtaining the null point a;determined by the position of the coils in the variable couplingtransformers of the improved circuit above described.

In solving the problem set up in Figure 14 another procedure could havebeen followed. With the azimuth indicator scale set at 0,'the pilotcould have turned the trainer until a null was obtained in the signalcircuit. The trainer would then be headed for the station or away fromthe station. A 90 turn would'have indicated to the pilot the directionof the station and then the course to the station determined and thetrainer turned and theoretically flown over the station.

Referring to the problem set-up illustrated in Figure 15, a map is setup for the determination of flxes from two stations indicated at Ill and2i i. The coast line shown on the map is that of Florida.

The automatic recorder tracer wheel is set at a location designated inFigure 15 as III. This location is unknown to the pilot and is oil! thesouthwest coast of Florida. The trainer is headed in the directionindicated by the arrow at this location at an angle of 320. The problemfor solution by the pilot is to first advise the instructor whichstation he is going to take a bearing on. then to take the bearing. and'to proceed likewise with taking a bearing on the other station. andthen by calculation to determine his own position relative to these twostations.

In the particular case assuming that the pilot undertakes to take abearing on the Miami station M which is indicated in Figure 15 at 2| I.According to the extended scale the instructor will set the flightcourse scale casing II that the flight course scale will read 258.Inasmuch as the pilot is headed at 320 the bearing observed by him willthen be 62 or 118. This is indicated in the readings of the flightcourse scale and asi- The pilot muth indicator in the upper right handportion of Figure 15. The pilot then calls the instructor by theinter-phone circuit and advises a bearing on KW (Key West) which isdesignated at 210 in Figure 15 of the drawings. The instructor then setthe flight course scale casing 95 sothat the flight course scale withreference to the pointer I06 will indicate the reading which the tracerwheel on the map assumes with respect to station 2H1, which is 15. Theheading of the trainer is still 320". The pilot's bearing on the azimuthindicator after the instructor has set the flight instructor can thencompare the pilot's map withhis own in order to determine the accuracyof the hearings, or the pilot may repeat his bearings from therespective station and the instructor can record them on his map inorder to determine the exact position from the plotted position.

As above indicated, in the solution of problems the azimuth scalereading is obtained by the pilot through the null point reached in thesignal circuit after the instructor has et the flight course scale atits true bearing.

It should be noted that the problems described in Figures 14 and 15 donot necessarily apply to use with trainer adaptation. As to the problemin Figure 15, the use of two tuning units similar to those described onthe automatic recorder and the azimuth indicator, without necessarilyusing the transformer unit attached to an automatic recorder, may beutilized. Problems may be solved by setting on the instructor's tuningunit settings which may be worked out ahead of the actual instructiontime and tabulated for use in the student instruction operation.

A problem such as presented in Figure 15 may be changed to include theinstruction of ground personnel or fixed station personnel, in the artof taking bearings and determining fixes on mobile stations or remotefixed stations. In such cases the instructor will have a pair of tuningunits similar to the transformers above described for each student,representing some Dre-selected ground station point. A group of stationsmay take a bearing on the same station at the same time withoutinterference with each other. In the set-up shown in Figure 15 a studentat station 2 and a student at station 210 may take bearings at the sametime providing the instructor has a separate tuning unit for eachstation. By communicating the bearings to each other an exact fix may bedetermined by plotting-the bearings on. a map. Such instruction is ofparticular advantage to dispatchers in aircraft work and to compassstation personnel on the ground.

Referring to Figures 1, 3, 4 and 5 of the drawings, mechanism is thereinillustrated in association with the flight course scale casing of anautomatic recorder for rendering positioning of the flight course scalefully automatic. With this arrangement the compass or bearings taken atall times will be exact without the necessity of the instructorresetting the flight course scale.

The operation of the automatic flight course 10 and is horizontallypositioned over the desk. At its outer end it is provided with a pivotpoint or axis member 252 on which a channel-shaped track 255 ispivotally mounted and horizontally positioned".- Fixed to the lflightcourse scale housing 95 are diametrically opposed vertically positionedarms or standards 254 and I55, which at their upper ends slidably flt inthe downwardly facing channel of the guide member 253. For correctoperation, the axial point 252 must be located directly over the stationon the map located on the instructorls table. As the automatic recordermoves over the map ,responsive to pilot's actuation of the trainer thetrack 253 will rotate on the axis 252 around the station and at any timewill represent a radial line with reference to the map. The bearingstaken by the pilot will be correctly set up at any instant by virtue ofthe movement of the guide member 253 responsive to automatic recorderactuation, due to the slidable connection of the standards 25! and 255in the track 253. With this apparatus the instructor need only observethe course of the automatic recorder and to correct for the propersignal intensities relative to distance from the station, and to theproper course signal identification. With this arrangement of course theflxed reference pointer must be removed from the automatic recorder.

We wish it to be distinctly understood that while the direction flndingcharacteristics of this invention are shown as related to a trainer,they may be used entirely independent of a trainer, and a signal sourceother than that usually used with a Link" trainer may be used. Theinvention so far as the electrical hook-up with the variable couplingtransformers is concemedmay be ,used for radio navigation instruction,and other demonstrating and instructing purposes.

Various changes in the structural features of this invention, therearrangement thereof, and changes made to the circuit and applicationof the structure of the invention, as well as changes in the modes andmethods of construction may be made to the invention as herein shown anddescribed, without departing from the spirit of the invention or thescope of the claims.

We claim:

1. An apparatus for instructing and training in flying by radionavigation comprising a grounded trainer controllable as to direction,means remote from the trainer for indicating the assumed bearing of thetrainer with respect to a simulated broadcasting station position, meansin said trainer for receiving signals simulating loop-antenna-receivedradio signals as received by the loop antenna of an aircraft in actualflight, means for creating and transmitting such scale resetting device,indicated at M is as follows: A supporting arm 250 is mounted upon asuitable standard 25L It may be positioned upon the instructor's desk,as shown in Figure 1,

signals of an intensity variable in accordance with the assumed bearingof the trainer with respect to the broadcasting station position, meansin said creating and transmitting means for varying the intensity ofsaid signals according to the assumed heading of the trainer, means insaid signal receiving means in the trainer for tuning the intensity ofthe signals received, and azimuth indicating means in said trainerconnected to said tuning means and operable therewith.

2. An electrical signalling apparatus forinstruction in the art ofnavigation by means of radio comprising a trainer having a receivingstation, means at said receiving station for aurally receiving signals,a transmitting station, means at said transmitting station for creatingand transmitting to the receiving station signals simulating signalsfrom a real transmitting or broadcasting station, means for transmittingsaid signals according to the assumed bearing of the trainer from theradio station being simulated, and means in the trainer for determiningthe assumed hearing from the trainer of the location of the real stationwhose signals are being simulated, said means comprising a visualbearing indicator and means for controlling the intensity of the signalsreceived and a single control for operating both the indicator and signaintensity controlling means.

3. An electrical signalling apparatus for radio navigational instructionin training devices comprising a receiving station in the trainingdevice including an azimuth scale and a pointer movable over saidazimuth scale, an electrical transmitting signal source remote from thereceiving station and under the operation of an instructor for thetransmission of signals varying in intensity according to the assumeddirection of the training device with respect to a simulated radiotransmitting station position, and an electroresponsive aural signalreceiving means at the receiving station, said electroresponsive' signalreceiving means being connected with the signal transmitting means forreceiving signals therefrom and including 'means for changing theintensity of the signals emitted by the receiving means operativelyconnected with the pointer, and means connected to the ointer and signalintensity changing means in the receiver for enabling the student tosimultaneously tune the intensity of the signal received to the maximumor null intensity of the signal from said transmitting means and changethe position of the pointer.

4. An apparatus for instruction and training in flight by radiocomprising a trainer controlable as to direction, means in said trainerfor aurally receiving signals simulating radio signals broadcast toairplanes in actual flight, an

azimuth indicator in said trainer having a scale and a pointer. thepointer being operatively connected to said signal receiving means forvarying the intensity of the signals as it is rotated over the scale,and means for creating and transmitting signals to said receiving'meansin accordance with the assumed bearing of the trainer from the locationof the real radio station being simulated by varying the intensity ofsuch signals.

5. An apparatus for the instruction of radio aerial navigationcomprising a ground trainer having means for directional controlthereof. an automatic recorder remote from the trainer and movable overa chart having a point thereon designating the position of a radiotransmittin station, said recorder having means of forward 12 ceivingmeans, and a control in the trainer for tuning. the intensity of thesignal received to maximum or null intensity and .simultaneouslychanging the reading of said bearing indicating instrument.

6. In an electrical signalling system for the instruction of radionavigation the combination of an electrical signal transmitting source,an aural signal receiver, a variable coupling transformer connected withthe signal transmitting station, means for operating said transformerfor varying the intensity of the signal transmitted, a variable couplingtransformer connected with said signal receiver, means for operatingsaid last mentioned ".cansformer for varying the intensity of the signalemitted by said receiver, and means. wiring the variable couplingtransformers of said transmitting and receiving stations.

7. In an electrical signalling system for the instruction of radionavigation the combination of an electrical signal transmitting source,an aural signal receiver, a variable coupling transformer connected withthe signal transmitting station, means for operating said transformerfor varying the intensity of the signal transmitted, a variable couplingtransformer connected with said signal receiver, means for operatingsaid last mentioned transformer for varying the intensity of the signalemitted by said receiver, means wiring the variable couplingtransformers of said transmitting and receiving stations, bearingindicating-instrument means having a movable element connected with thevariable transformer of the signal receiver, and a control forsimultaneously operating the last mentioned variable transformer andmovable element of the bearing indicating means.

8. The apparatus setforth in-claim 2 in which means are also providedfor changing the intensity of the signals received by the receivingmovement and means responsive to directional control movement of thetrainer for indicating the assumed pat "of travel 01' the trainer,electrical signal tr smitting means remote from the trainer, electricalsignal receiving means in the trainer for aurally receiving the signalof the .transmitting means, said receiving means inmeans according tochanges in the assumed heading of the trainer.

9. An electrical system for use in conjunction with grounded aviationtrainers and the like for instructing students in navigation by radiocomprising a trainer having a seat for a student, an aural signalreceiver for use by a student in the seat. a visual indicator includingazimuth indicating means arranged to be viewed by the student in theseat, an electrical transmitting signal source connected to said auralsignal receiver through means for controlling the strength of thesignals emitted .by said signal receiver, and three separately operablemeans for operating the means for controlling the strength of thesignals emitted by the signal receiver, at least one of said separatelyoperablemeans being under the control of the student and connected tosaid azimuth indicatin meansto change the reading of the samesimultaneously with operation of said separately operable means.

10. The structure set forth in claim 9 in which the second separatelyoperable means is operated according to the assumed bearing of thetrainer from a simulated radio transmitting station position.

' 11. The structure set forth in claim 10 in which the third separatelyoperable means is operated according to the assumed heading of thetrainer.

AHLERT P. STUHRMAN. CHARLES w. -McKEE.

(References on following Pile).

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date Pollen Jan. 5, 1915 Rowell Jan.3, 1928 Link Sept. 29, 1931 Link Nov. 23, 1937 Crane Mar. 15, 1938 LinkMay 31, 1938 Dunmore June 7, 1938 Patin Mar. 28, 1939 Koster July 4,1939 Number Number OTHER REFERENCES Air Corps News Letter, v01. 21, No.6, March 15,

Aeronautics Bulletin No. 27, July 1, 1937.

